1. Field of the Invention
The present invention relates to a video cassette tape recorder (VCR) equipped with a cassette loading device of the front loading type, and more particularly to a cassette loading device equipped with an erroneous insertion preventing device.
2. Description of the Prior Art
Generally, a recording and reproducing apparatus such as a VCR for a magnetic tape cassette is equipped with a cassette loading device for feeding a tape cassette between a loading/ejecting position and a recording/reproducing position and determining the position of the tape cassette at each of the operation positions. In particular, in a recording and reproducing apparatus provided at its front wall with a loading/ejecting opening for a tape cassette, a cassette loading device of the front loading type is widely used which includes a cassette holder for holding the tape cassette to be loaded and ejected under a condition that the tape cassette is transversely laid in parallel to the direction that the tape cassette is fed.
Such a cassette loading device of the front loading type is illustrated in FIG. 16. This cassette loading device includes a cassette holder 2 for holding a tape cassette 1 to be loaded and ejected under a condition that the tape cassette is transversely laid, a supporting base body 3 for receiving the cassette holder 2 and supporting it to be movable between a cassette loading/ejecting position and a recording/reproducing position, and a driving mechanism for moving the cassette holder 2 in the supporting base body 3. The cassette holder 2 comprises a frame 4 for supporting the upper and lower surfaces of the tape cassette 1, and a pair of sliding side plates 5 downwardly extending from both lateral ends of the frame 4 to support both side surfaces of the tape cassette 1, respectively. Each sliding side plate 5 has a drive pin 6 and a pair of guide pins 7 so as to guide the cassette holder 2 in the supporting base body 3. The drive pin 6 and guide pins 7 are outwardly protruded from the outer surface of the sliding side plate 5. The supporting base body 3 has a pair of fixed side plates 8 downwardly extending from both lateral ends of a frame 9 to support both sliding side plates 5 of the cassette holder 2, respectively. Each of the fixed side plates 8 has a L-shaped guide slot 10 for receiving the drive pin 6 protruded from each corresponding sliding side plate 5 and a pair of L-shaped guide slots 11 for receiving the guide pins 7 protruded from each corresponding sliding side plate 5, respectively. Each of the drive pin 6 is outwardly protruded through the guide slot 10 of each corresponding fixed side plate 8 so that its protruded end is coupled to a drive lever 12 connected to a drive mechanism not shown. When the tape cassette 1 is to be fed, each drive pin 6 moves along each corresponding guide slot 10 by the rotation of a shaft 13 of the drive levers 12. Since the guide pins 7 are also engaged in the corresponding guide slots 11, respectively, the cassette holder 2 moves along a L-shaped path while it is supported at three fulcrums.
For feeding the tape cassette between the loading/ejecting position and the recording/reproducing position, the cassette loading device of the front loading type performs a movement operation obtained by a horizontal movement and a vertical movement carried out along the L-shaped path defined by the guide slots 10 and 11. This movement operation enables the tape cassette 1 received in the cassette holder 2 to be engaged with and disengaged from heads and reels for recording/reproducing operations arranged at the recording/reproducing position. Generally, two guide pins 7 are arranged on each sliding side plate 5 of the cassette holder 2 at positions apart different radiuses from the drive pin 6, respectively, so that the guide pins 7 follow accurately the drive pin 6 as the drive fulcrum of the cassette holder 2, in particular, at the curved portion of the L-shaped path, thereby preventing an undesirable operation of the cassette holder 2 such as a slanting phenomenon. As a result, each fixed side plate 8 of the supporting base plate 3 has three guide tracks each of which guides each corresponding pin along the L-shaped path. Among the guide tracks, the guide track for the drive pin 6 is constituted by a bottom-reinforced slot for a maintenance of the strength of the fixed side plate 8. The three guide tracks are formed on the fixed side plate 8 at independent positions so that they do not cross one another in order to accurately and smoothly guide the pins.
Such independent arrangements of the guide tracks on the fixed side plate causes inevitably an increase area of the fixed side plate. Furthermore, the spaces among the three pins of the cassette holder are increased, thereby resulting in an increased area of the sliding side plate. As a result, there is a limitation on compactness in the conventional cassette loading device. This causes a difficulty to provide a recording and reproducing apparatus with a compact construction.
The travel distance of the tape cassette between the loading/ejecting position and the recording/reproducing position is determined by the construction of the recording and reproducing apparatus. For providing a cassette loading device with a more compact construction, the three guide tracks should be integrated on a small area of the fixed side plate because the above-mentioned travel distance can not be varied. To this end, a cross arrangement of the guide tracks may be conceived. However, such a cross arrangement encounters a difficulty to accurately and smoothly guide the drive pins and the guide pins of the cassette holder at cross portions of the guide tracks.
When the tape cassette is erroneously inserted in the cassette loading device, for example, under a condition that it is inverted or longitudinally laid, precise elements of the internal mechanism of the VCR may be damaged. For avoiding such a damage, the conventional cassette loading device has erroneous insertion preventing means equipped in the cassette holder. An example of such erroneous insertion preventing means is disclosed in Japanese Utility Model Laid-open Publication No. Heisei 2-44376. However, this device is adapted to mainly utilize erroneous insertion preventing grooves provided at VHS type video tape cassettes. There has not been proposed any erroneous insertion preventing device for 8 mm video tape cassettes the use of which is on an increasing trend.